General Physiology Overview

General Physiology

• The human body comprises a variety of molecules
• Water (H₂O) accounts for about 60% of total body weight
• Proteins make up about 18% of body weight
• Lipids (fats) constitute around 15% of body weight
• Minerals represent roughly 5% of body weight.
• Nucleic acids (DNA and RNA) are essential components
• Carbohydrates account for less than 1% of body weight, stored in liver and muscles as glycogen

Body Planes

• Sagittal plane
• Coronal plane
• Transverse plane

Organ Systems

• Integumentary system (Skin, hair, nails)
• Skeletal system (Bones, joints)
• Muscular system (Skeletal muscles)
• Nervous system (Brain, spinal cord, nerves)
• Endocrine system (Glands secreting hormones)
• Cardiovascular system (Heart, blood vessels)
• Lymphatic system (Lymph nodes, lymphatic vessels)
• Respiratory system (Lungs, airways)
• Digestive system (Stomach, intestines, liver)
• Urinary system (Kidneys, bladder)
• Reproductive system (Ovaries/testes, associated organs)

Total Body Water (TBW)

• TBW comprises 55-60% of body weight in adult males
• Percentage varies with age, sex, and obesity
• Adult females typically have 50-55% TBW
• A 70kg man has approximately 42 liters of body water

Distribution of Body Water

• Intracellular fluid (ICF) is about 40% of body weight, located inside cells
• Extracellular fluid (ECF) is about 20% of body weight, outside cells (interstitial fluid 15%, plasma 5%)

Variations in Body Water

• Age: Infants (75-80%), Children (65-70%), Adults (Males 60%, Females 55%), Elderly (50-55%)
• Sex: Males (generally 60%) have more muscle mass; females (50-55%) have more body fat

Body Composition

• Muscle mass correlates with higher body water
• Body fat is associated with lower body water

Health Status

• Dehydration reduces body water content
• Overhydration increases body water content

Function of Body Water

• Building material: Essential for all cells especially during growth
• Solvent: Dissolves ionic compounds, glucose, and amino acids
• Carrier: Transports nutrients and removes wastes, facilitating exchanges between cells, interstitial fluid and capillaries
• Thermoregulation: Water's high heat capacity helps regulate body temperature
• Lubricant/Shock absorber: Forms fluids for joints, protecting them

High Extracellular Fluid Contents

• Na+, Cl-, Bicarbonate
• Ion Concentrations include:
  • Na+
  • K+
  • Ca++
  • Mg++
  • Cl-
  • HCO3
  • Phosphates
  • SO4
  • Glucose
  • Amino acids
  • Cholesterol
  • Phospholipids
  • Neutral fat
  • PO₂
  • PCO₂
  • pH
  • Proteins

High Intracellular Fluid Contents

• K+, Mg++, pH, Proteins

Transport Across the Cell Membrane

• Mechanisms include passive and active transport, as well as bulk transport.

1- Passive Transport

• Movement down the concentration gradient
• Does not require cellular energy (ATP)
• Includes simple diffusion, facilitated diffusion, and osmosis.
• Influenced by factors like concentration gradient, temperature, diffusion distance, surface area, molecular size, solubility

Types of Passive Transport

• Simple Diffusion: Small molecules move directly through the lipid bilayer
• Facilitated Diffusion: Larger molecules use protein channels or carriers
• Osmosis: Movement of water across a semipermeable membrane

Factors Affecting Diffusion

• Concentration Gradient: Greater difference leads to faster diffusion.
• Temperature: Higher temperature results in faster diffusion.
• Diffusion Distance: Thicker membranes slow diffusion.
• Surface Area: Larger areas allow for more diffusion.
• Molecular Size: Smaller molecules diffuse faster.
• Solubility: Lipid-soluble substances diffuse more readily.

2- Active Transport

• Movement against the concentration gradient
• Requires cellular energy (ATP)
• Types:
  • Primary Active Transport: Direct use of ATP to transport molecules. Example: Na+/K+-ATPase pump
  • Secondary Active Transport: Uses energy from primary active transport to transport another molecule. Example: Sodium-glucose co-transporter

Functions of Na+/K+-ATPase Pump

• Resting Membrane Potential
• Regulation of Cell Volume
• Nerve Impulse Transmission
• Muscle Contraction

3- Bulk Transport

• Movement of large molecules/particles via vesicles.
• Types:
  • Endocytosis: Cell membrane engulfs materials into vesicles (Phagocytosis and Pinocytosis and Receptor-Mediated)
  • Exocytosis: Vesicles fuse with cell membrane, releasing contents outside the cell. Example: secretion of neurotransmitters from neurons

Explore the fundamental aspects of human physiology, including the composition of the body and the various organ systems. Understand the role of molecules like water, proteins, and lipids in body weight, as well as the different anatomical planes. This quiz will enhance your knowledge of how the human body functions.